High-Value Biomass-Derived 2,5-Furandicarboxylic Acid Derivatives

Research Article pubs.acs.org/journal/ascecg

High-Value Biomass-Derived 2,5-Furandicarboxylic Acid Derivatives Obtained by a Double Decarboxylative Cross-Coupling Franklin Chacón-Huete,† Daniel Mangel,† Maythem Ali,† Anthony Sudano,† and Pat Forgione*,†,‡ †

Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, QC H4B 1R6, Canada Centre for Green Chemistry and Catalysis, Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada

‡

S Supporting Information *

ABSTRACT: A new methodology was developed employing biomass-derived 2,5-furandicarboxylic acid to produce 2,5-diaryl furans in good to excellent yields through palladium-catalyzed double decarboxylative cross-couplings. Various aryl halides were successfully evaluated as coupling partners. The present work contributes to the development of useful methodologies employing biomass-derived starting materials for the chemical synthesis industry.

KEYWORDS: Biomass, Cross-coupling, Decarboxylation, Catalysis, Palladium

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redox systems23−25 have been reported. These transformations would yield a type of disubstituted furan that is present in a variety of pharmaceutical targets (Scheme 1). The decarboxylative cross-coupling of furoic acid has proven to be challenging, in comparison with those of other heteroaromatic carboxylic acids, as discussed by Forgione et al., who reported the decarboxylative cross-coupling reaction between 2-furoic acid and bromobenzene with a 40% yield26 (Scheme 2). The same reaction using modified conditions was reported by Gooßen et al., with a yield of 38%.32 The only two reports of a decarboxylative cross-coupling of furoic acid produced a single arylation in moderate yields (Scheme 2).26,32 When these conditions were applied to the double-decarboxylative cross-coupling between FDCA and bromobenzene, no diarylation product formation was observed (Scheme 2). A systematic optimization pathway was followed toward a double-decarboxylative cross-coupling arylation of FDCA.

INTRODUCTION The ability of the global fine-chemicals industry to support a growing and developing world population is compromised by its heavy reliance on nonrenewable petrochemical feedstocks. As such, there is significant economic, social, and scientific interest in biobased, sustainable feedstocks for the production of value-added chemicals.1 In 2004, the U.S. Department of Energy released a list of compounds derived from biorefining carbohydrates with the purpose of stimulating and focusing research and industrial efforts on processes to convert lignocellulosic biomass into chemical feedstocks.2 That list included 2,5-furandicarboxylic acid (FDCA) and triggered a significant amount of research concerning the production of FDCA from fructose3,4 and its subsequent use as a monomer in the production of industrially important condensation polymers.5 The success of those efforts, which notably include a BASF/ Avantium joint 50000 MT/year FDCA plant,6 an ADM− DuPont platform,7 and recent efforts by MetGen,8 suggests that FDCA will evolve into a widely available, cost-effective raw material. As such, chemical transformations of FDCA into more complex, high-value structures are expected to be of broad interest. Palladium-catalyzed reactions have proven to be effective for creating C−C bonds, but the classical approach requires prefunctionalization of the starting materials, which are often highly reactive organometallic compounds. Modification of heteroaromatic carboxylic acids through the highly regioselective decarboxylative cross-coupling reaction9−22 and photo© 2017 American Chemical Society

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RESULTS AND DISCUSSION Decarboxylative cross-coupling conditions previously reported26 were used as the starting point for the optimization of the diarylation of FDCA with p-bromobenzotrifluoride as a coupling partner. A variety of palladium catalysts were tested for their utility in the double cross-coupling reaction, as shown Received: April 24, 2017 Revised: June 6, 2017 Published: July 5, 2017 7071

DOI: 10.1021/acssuschemeng.7b01277 ACS Sustainable Chem. Eng. 2017, 5, 7071−7076

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Scheme 1. Reported Examples of 2,5-Disubstituted Furans with Pharmaceutical Applications: Minor Groove DNA Binder,27 Estrogen Receptor Antagonist,28 and Antiprotozoal Agent29

Scheme 2. Previously Reported26 Decarboxylative Cross-Coupling of 2-Furoic Acid and First Attempt at the DoubleDecarboxylative Cross-Coupling of FDCAa

a Reaction conditions (same as reported): 2-furoic acid/bromobenzene, 2:1; FDCA/bromobenzene, 1:1; Pd[P(t-Bu)3]2, 5 mol %; Cs2CO3, 1.5 equiv; n-Bu4NCl, 1.0 equiv; DMF, 0.2 M; microwave (μw), 170 °C, 8 min.26

in Table 1. No difference was observed when employing PdII versus Pd0 sources (entries 1, 4, and 8 vs 2, 5, and 6 in Table 1). An increase in catalyst loading from 5% to 15% improved the product yield substantially (entry 8 vs 9). Pd(dba)2 at a higher loading provided the best results among the palladium sources screened and was selected for subsequent optimization of additional parameters. Multiple solvent systems were studied; high-boiling-point, polar aprotic solvents such as dimethylacetamide (DMA) and dimethylformamide (DMF) provided the best results with product yields ranging from 20% to 25%. Other solvents including isopropanol, water, ethanol, and dioxane did not yield the desired product. DMA was used for subsequent optimization reactions. In all cases, the major byproduct obtained was the homocoupling of the aryl halide; nonetheless, a monoarylation was observed in small amounts for some cases [by gas chromatography/mass spectrometry (GC/MS)], which suggests that the second decarboxylation occurs faster that the first one. Base optimization was done in the presence of 1 equiv of nBu4NCl, as suggested by previous reports (see Table 2).16 tertButoxides (entries 1 and 2) yielded only trace amounts of the desired product, as observed by 1H NMR spectroscopy. An organic tertiary amine (entry 3) gave a complex mixture of products and none of the desired product. Given the general

Table 1. Optimization of the Palladium Source in the Reactiona

entry

Pd source

Pd content (mol %)

1 2 3 4 5 6 7 8

Pd(PPh3)4 Pd(OAc)2 Pd[P(t-Bu)3]2 Pd(acac)2 PdI2 Pd(TFA)2 Pd(dba)2 Pd(dba)2

10 15 15 15 15 15 5 15

ligand

ligand content (mol %)

yield (%)

− JohnPhos − JohnPhos JohnPhos JohnPhos JohnPhos JohnPhos

0 30 0 30 30 30 10 30

0 14 8 10 0 17 9 20

a Reaction conditions: 1.0 equiv (0.2 mmol) of FDCA, 2 equiv of pbromobenzotrifluoride, 1 equiv of n-Bu4NCl, 3 equiv of Cs2CO3, 2 mL of DMF. Reaction in μw at 170 °C for 8 min. *For those Pd sources not containing phosphine ligands, Pd was added at a 1:2 molar ratio of Pd to JohnPhos.

utility of Cs2CO3 in this reaction and previous reports on related reactions,26,30,31 K2CO3 was evaluated (entry 4), but no 7072


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Table 3. Optimization of the Ligand Used in the Reactiona

Table 2. Optimization of the Base Employed in the Reactiona

entry

base

additive

yield (%)

1 2 3 4 5 6 7b 8 9 10c

KOtBu LiOtBu N-Et-iPr2 K2CO3 Ag2CO3 Ag2CO3 Ag2CO3 Ag2CO3/KOH (1:1) Cu2(OH)2CO3 Ag2CO3

n-Bu4NCl n-Bu4NCl n-Bu4NCl n-Bu4NCl n-Bu4NCl none none n-Bu4NCl n-Bu4NCl none

trace trace 0 trace 30 36 34 5 0 44

entry

ligand

yield (%)

1 2 3 4 5 6 7 8

JohnPhos P(Cy)3 t-BuMePhos dppf MePhos PPh3 P(Cy)3HBF4 P(t-Bu)3

44 trace 40 30 45 14 trace trace

a Reaction conditions: 1 equiv (0.2 mmol) of FDCA, 4 equiv of pbromobenzotrifluoride, 0.2 equiv of Ag2CO3, 15 mol % of Pd(dba)2, 30 mol % of JohnPhos, and 2 mL of DMA.

a

Reaction conditions: 1 equiv (0.2 mmol) of FDCA, 2 equiv of pbromobenzotrifluoride, 1 equiv of n-Bu4NCl, 3 equiv of base. bOnly 2 equiv of Ag2CO3, 15 mol % of Pd(dba)2, 30 mol % of JohnPhos, and 2 mL of DMA. cReaction carried out at 200 °C with 4 equiv of aryl bromide.

Table 4. Optimization of the Number of Equivalents of Ag2CO3 and n-Bu4NCl Used in the Reactiona

product was observed. With inspiration from the approaches of Gooßen and co-workers11,12,32 and Becht and co-workers,13,33 bimetallic systems were evaluated. A silver-containing base, Ag2CO3, had a positive impact on the product yield (entry 5), which suggests that the decarboxylation is the rate-limiting step.33 Control experiments were done using Cs2CO3 as the base and silver salts (AgBF4, AgOTf, AgCl) as additives, but none of these systems yielded the desired product. In contrast to the results presented here for FDCA, in which the highest yields occurred at an elevated temperature of 200 °C (entry 10), the reports of Gooßen et al.32 indicated that silvermediated systems allow palladium-catalyzed protodecarboxylation to proceed at lower temperatures. However, when this reaction was carried out at 170 °C, only a 16% yield was obtained. Interestingly, decreasing the number of equivalents of base had no significant impact on the yield (entries 6 and 7). Ag2CO3 and a 200 °C reaction temperature were used in subsequent optimization reactions, and the number of equivalents of aryl halide was increased to 4. In agreement with work reported by others, the screening of different ligands indicated that bulky trisubstituted phosphines provided the highest yields (Table 3).34 Two very similar phosphines, MePhos and JohnPhos, were employed in the subsequent optimization reactions. Given earlier results indicating that reducing the number of equivalents of silver carbonate did not have a substantial impact on the yield (Table 2, entries 6 and 7), a base and additive loading and ratio optimization was conducted (Table 4). The highest yields were achieved with 1.5 equiv of each of these components in a 1:1 ratio, which impressively provided the corresponding diarylated product in 80% yield (entry 3) without the need to employ excess aryl iodide. With the final optimized conditions, the reaction scope was evaluated employing a range of coupling partners (Table 5). The reaction gave satisfactory to excellent yields for a wide scope of aryl halides. Electron-defficient aryl halides provided the highest yields when JohnPhos was employed as the ligand. For the neutral and electron-rich coupling partners, the best results were obtained when MePhos was used instead, with the

entry

Ag2CO3(equiv)

n-Bu4NCl (equiv)

yield (%)

1 2 3 4 5

3.0 2.0 1.5 1.0 3.0

0.0 1.0 1.5 2.0 4.0

42 38 80 47 23

a

Reaction conditions: 1 equiv (0.2 mmol) of FDCA, 4 equiv of pbromobenzotrifluoride, varying Ag2CO3 and n-Bu4NCl, 15 mol % of Pd(dba)2, 30 mol % of JohnPhos, and 2 mL of DMA.

other parameters remaining the same. Lower yields were obtained for ortho and meta isomers (entries 1 vs 5 and 8 vs 9) when compared to their para homologues, which is potentially attributed to the steric effects of the substituents. When coupling partners with phenol groups were used, the reaction did not yield the desired compound. Using tosylates or chlorides as coupling partners proved to be ineffective for the reaction to occur. As is usually observed in cross-coupling reactions involving aryl halides, the aryl iodides provided higher yields than their bromide analogues, likely because of the more facile oxidative addition of Pd(0) into the Csp2−I in comparison to the Csp2−Br.35,36 To increase the utility of this method, the possibility of recycling the silver carbonate based on a protocol employed by Tan et al.37 was evaluated. Promising results were obtained in small-scale experiments, indicating that this could be accomplished with little effect on the subsequent cross-coupling yields (Table 6).

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CONCLUSIONS In summary, a double-decarboxylative cross-coupling reaction has been developed that employs biomass-derived 2,5furandicarboxylic acid as the starting material. The scope of the reaction proved to be broad, and the yields for the formation of two new carbon−carbon bonds ranged from moderate to excellent. The presented work suggests that the efficient and innovative use of small molecules coming from renewable feedstocks is one of many ways in which sustainable 7073


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ACS Sustainable Chemistry & Engineering Table 5. Scope of the Reaction under the Optimized Conditionsa

a Reaction conditions: 1 equiv (0.2 mmol) of FDCA, 4 equiv of aryl halide, 1.5 equiv of Ag2CO3, 1.5 equiv of n-Bu4NCl, 15 mol % of Pd(dba)2, 30 mol % of JohnPhos (a, using MePhos instead), and 2 mL of DMA.

Table 6. Effect of Recycling Ag2CO3 in the Reactiona

cycle

yieldb (%)

recovery of Ag2CO3 (%)

1 2 3

77 81 76

84 84 81

mmol) were added to a 2.0 mL conical microwave vial equipped with a spin-vein. Aryl halide (0.8 mmol) and anhydrous DMA (2 mL) were added to the mixture, and the vial was sealed. The mixture was heated in a microwave at 200 °C for 8 min. The reaction was mixture was cooled to 23 °C, and the crude product was diluted with EtOAc (15 mL) and washed with saturated NaCl (2 × 20 mL) and saturated NaHCO3 (1 × 20 mL). The combined organic phases were dried over Na2SO4 and filtered, and the solvent was evaporated under reduced pressure. The crude mixture was purified by column chromatography to yield the desired product.

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a

Reaction conditions: 1 equiv (0.2 mmol) of FDCA, 4 equiv of pbromobenzotrifluoride, 1.5 equiv of Ag2CO3, 1.5 equiv of n-Bu4NCl, 15 mol % of Pd(dba)2, 30 mol % of JohnPhos, and 2 mL of DMA. b Calculated from 1H NMR spectrum, using trimethoxybenzene as an internal standard.

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b01277. Experimental procedures, purification methodologies, and conditions used; spectral information for all compounds synthesized including 1H NMR, 13C NMR, and high-resolution mass spectra (PDF)

chemistry can be developed. The use of biomass as a resource for building blocks rather than biofuels is an area that needs to be explored, but enourmous efforts are being made toward the advance of sustainable chemistry.

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ASSOCIATED CONTENT

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EXPERIMENTAL SECTION

General Procedure for the Preparation of the 2,5Disubstituted Furans. 2,5-Furandicarboxylic acid (0.2 mmol), Ag2CO3 (0.3 mmol), n-Bu4NCl (0.3 mmol), Pd(dba)2 (0.03 mmol), and ligand (either JohnPhos or MePhos, as indicated in Table 5) (0.06

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. 7074


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Pat Forgione: 0000-0002-6029-2194 Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by the Natural Sciences and Engineering Research Council (NSERC) of Canada and Le Fonds de Recherche du Québec, Nature et Technologies (FRQNT). Support was also kindly provided by the Centre for Green Chemistry and Catalysis (CGCC), Le Réseau Québécois de Recherche sur les Médicaments (RQRM), and Concordia University. The authors offer special thanks to Fei Chen, Cindy Buonomano, and Fadıl Taç for their valuable advice.

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ABBREVIATIONS FDCA, 2,5-furandicarboxylic acid; μw, microwave REFERENCES

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High-Value Biomass-Derived 2,5-Furandicarboxylic Acid Derivatives

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